[dv] V2S Coverage Implementation

ctopal · ctopal · commit 09d3d61015c4 · 2022-11-02T11:07:21.000Z
This commit adds coverpoints and crosses for security countermeasures
implemented in the design.

Signed-off-by: Canberk Topal &lt;ctopal@lowrisc.org&gt;
diff --git a/doc/03_reference/coverage_plan.rst b/doc/03_reference/coverage_plan.rst
@@ -299,6 +299,30 @@ Basic read/write functionality must be tested on all implemented CSRs.
 CSRs addresses do not need to be crossed with the variety of CSR instructions as these all use the same basic read & write interface into ``ibex_cs_registers``.
 Coverage of the above points will be sampled at the ``ibex_cs_registers`` interface (as opposed to sampling CSR instructions).
 
+Security Countermeasures
+^^^^^^^^^^^^^^^^^^^^^^^^
+For more detail about each security countermeasure in Ibex see :ref:`security`
+
+* ``cp_data_ind_timing`` - Enabling/Disabling "Data Independent Timing" feature.
+
+* ``cp_data_ind_timing_instr`` - Executing each instruction category while data independent timing feature is enabled.
+
+* ``cp_dummy_instr_en`` - Enabling/Disabling "Dummy Instruction Insertion" feature.
+
+* ``cp_dummy_instr_mask`` - Frequency of injection for the dummy instructions.
+
+* ``cp_dummy_instr_type`` - Type of the injected dummy instruction.
+
+* ``cp_dummy_instr`` - Executing each instruction category while dummy instruction insertion feature is enabled.
+
+* ``cp_rf_a_ecc_err``, ``cp_rf_b_ecc_err`` - Register file integrity (ECC) fault is seen for port A/B.
+
+* ``cp_icache_ecc_err`` - ICache has seen an integrity (ECC) fault.
+
+* ``cp_lockstep_err`` - Lockstep glitch fault seen.
+
+* ``cp_rf_we_glitch_err`` - Register file write enable glitch fault seen.
+
 Miscellaneous
 ^^^^^^^^^^^^^
 Various points of interest do not fit into the categories above.
@@ -348,3 +372,7 @@ There must be a documented reason a particular bin is added to the illegal or ig
 * ``pmp_iside_priv_bits_cross``, ``pmp_iside2_priv_bits_cross``, ``pmp_dside_priv_bits_cross``, PMP regions x permissions x access fail/pass x privilege level
 
   * Three crosses, one for each PMP channel (instruction, instruction 2 and data).
+
+* ``dummy_instr_config_cross`` - Dummy Instruction Type x Dummy Instruction Insertion Frequency to explore all possible configurations.
+
+* ``rf_ecc_err_cross`` - ECC Error on Port A x ECC Error on Port A to explore all possible combinations of reported ECC errors.
diff --git a/dv/uvm/core_ibex/fcov/core_ibex_fcov_if.sv b/dv/uvm/core_ibex/fcov/core_ibex_fcov_if.sv
@@ -15,7 +15,10 @@ interface core_ibex_fcov_if import ibex_pkg::*; (
   input debug_mode,
 
   input fcov_csr_read_only,
-  input fcov_csr_write
+  input fcov_csr_write,
+
+  input fcov_rf_ecc_err_a_id,
+  input fcov_rf_ecc_err_b_id
 );
   `include "dv_fcov_macros.svh"
   import uvm_pkg::*;
@@ -381,6 +384,10 @@ interface core_ibex_fcov_if import ibex_pkg::*; (
     (id_stall_type == IdStallTypeNone) && (id_stall_type_last != IdStallTypeNone) &&
     id_stall_type_last_valid;
 
+  // V2S Related Probes for Top-Level
+  logic rf_we_glitch_err;
+  logic lockstep_glitch_err;
+
   covergroup uarch_cg @(posedge clk_i);
     option.per_instance = 1;
     option.name = "uarch_cg";
@@ -423,6 +430,31 @@ interface core_ibex_fcov_if import ibex_pkg::*; (
     cp_id_stage_state : coverpoint id_stage_state;
     cp_wb_stage_state : coverpoint wb_stage_state;
 
+    // V2S Coverpoints
+    cp_data_ind_timing: coverpoint cs_registers_i.data_ind_timing_o;
+    cp_data_ind_timing_instr: coverpoint id_instr_category iff (cs_registers_i.data_ind_timing_o){
+      // Not certain if InstrCategoryOtherIllegal can occur. Put it in illegal_bins for now and
+      // revisit if any issues are seen
+      illegal_bins illegal = {InstrCategoryOther, InstrCategoryOtherIllegal};
+    }
+
+    cp_dummy_instr_en: coverpoint cs_registers_i.dummy_instr_en_o;
+    cp_dummy_instr_mask: coverpoint cs_registers_i.dummy_instr_mask_o;
+    cp_dummy_instr_type: coverpoint if_stage_i.fcov_dummy_instr_type;
+    cp_dummy_instr: coverpoint id_instr_category iff (cs_registers_i.dummy_instr_en_o){
+      // Not certain if InstrCategoryOtherIllegal can occur. Put it in illegal_bins for now and
+      // revisit if any issues are seen
+      illegal_bins illegal = {InstrCategoryOther, InstrCategoryOtherIllegal};
+    }
+
+    cp_rf_a_ecc_err: coverpoint fcov_rf_ecc_err_a_id;
+    cp_rf_b_ecc_err: coverpoint fcov_rf_ecc_err_b_id;
+
+    cp_icache_ecc_err : coverpoint if_stage_i.icache_ecc_error_o;
+
+    cp_lockstep_err : coverpoint lockstep_glitch_err;
+    cp_rf_we_glitch_err : coverpoint rf_we_glitch_err;
+
     // TODO: MRET/WFI in debug mode?
     // Specific cover points for these as `id_instr_category` will be InstrCategoryPrivIllegal when
     // executing these instructions in U-mode.
@@ -673,6 +705,12 @@ interface core_ibex_fcov_if import ibex_pkg::*; (
       // Only care about specific debug CSRs
       ignore_bins ignore = !binsof(cp_csr_write) intersect {`DEBUG_CSRS};
     }
+
+    dummy_instr_config_cross: cross cp_dummy_instr_type, cp_dummy_instr_mask
+                                iff (cs_registers_i.dummy_instr_en_o);
+
+    rf_ecc_err_cross: cross cp_rf_a_ecc_err, cp_rf_a_ecc_err
+                                iff (id_stage_i.instr_valid_i);
   endgroup
 
   bit en_uarch_cov;
diff --git a/dv/uvm/core_ibex/tb/core_ibex_tb_top.sv b/dv/uvm/core_ibex/tb/core_ibex_tb_top.sv
@@ -161,6 +161,12 @@ module core_ibex_tb_top;
   `ASSERT(NoAlertsTriggered,
     !dut_if.alert_minor && !dut_if.alert_major_internal && !dut_if.alert_major_bus, clk, !rst_n)
 
+  assign dut.u_ibex_top.u_ibex_core.u_fcov_bind.rf_we_glitch_err =
+    dut.u_ibex_top.rf_alert_major_internal;
+
+  assign dut.u_ibex_top.u_ibex_core.u_fcov_bind.lockstep_glitch_err =
+    dut.u_ibex_top.lockstep_alert_major_internal;
+
   // Data load/store vif connection
   assign data_mem_vif.reset = ~rst_n;
   // Instruction fetch vif connnection
diff --git a/rtl/ibex_core.sv b/rtl/ibex_core.sv
@@ -1703,6 +1703,10 @@ module ibex_core import ibex_pkg::*; #(
   //////////
 
 `ifndef SYNTHESIS
+  // fcov signals for V2S
+  `DV_FCOV_SIGNAL_GEN_IF(logic, rf_ecc_err_a_id, gen_regfile_ecc.rf_ecc_err_a_id, RegFileECC)
+  `DV_FCOV_SIGNAL_GEN_IF(logic, rf_ecc_err_b_id, gen_regfile_ecc.rf_ecc_err_b_id, RegFileECC)
+
   // fcov signals for CSR access. These are complicated by illegal accesses. Where an access is
   // legal `csr_op_en` signals the operation occurring, but this is deasserted where an access is
   // illegal. Instead `illegal_insn_id` confirms the instruction is taking an illegal instruction
diff --git a/rtl/ibex_if_stage.sv b/rtl/ibex_if_stage.sv
@@ -681,6 +681,16 @@ module ibex_if_stage import ibex_pkg::*; #(
     assign fetch_ready = id_in_ready_i & ~stall_dummy_instr;
   end
 
+  //////////
+  // FCOV //
+  //////////
+
+`ifndef SYNTHESIS
+  // fcov signals for V2S
+  `DV_FCOV_SIGNAL_GEN_IF(logic [1:0], dummy_instr_type,
+    gen_dummy_instr.dummy_instr_i.lfsr_data.instr_type, DummyInstructions)
+`endif
+
   ////////////////
   // Assertions //
   ////////////////
